WO1999023748A1

WO1999023748A1 - Device and method for controlling converter and converter

Info

Publication number: WO1999023748A1
Application number: PCT/JP1997/003989
Authority: WO
Inventors: Keijiro Sakai; Kenji Kubo; Toshihiko Yamamoto
Original assignee: Hitachi, Ltd.
Priority date: 1997-10-31
Filing date: 1997-10-31
Publication date: 1999-05-14

Abstract

A converter which converts AC power into DC power by turning on/off a switching element is operated with a chopper at the time of starting the converter and, after the DC output voltage of the converter is boosted, with a PWM. When the converter is operated in such a way, no excessively large power supply current flows to the AC side, because the voltage across both ends of an AC reactor can be made lower.

Description

Specification

Converter control device and control method, and converter

The present invention relates to a method for starting a PWM converter. Background art

In a pulse width modulation (PWM) converter, an excessive power supply current flows at the start of switching from the diode rectification mode to the PWM converter control, so that the converter main circuit element is damaged and the overcurrent protection circuit malfunctions. There is a problem of work. As a solution to this problem, there is a technique described in Japanese Patent Application Laid-Open No. 1-160364. In this method, the DC voltage detection value at the output side of the converter is used as the DC voltage command before starting the converter, and the DC voltage command is gradually increased after starting up to the DC voltage command during steady-state operation of the converter. By reducing the deviation between the DC voltage command and the detected value by such processing, the power supply current amplitude command, which is the PI-compensated output of this deviation, is started to be reduced. This prevents the power supply current from becoming excessive. <In this conventional example, the power supply current amplitude command is reduced to a small value, so the power supply current for charging the smoothing capacitor is suppressed while charging to a predetermined DC voltage. it can. However, even if the power supply current amplitude command is reduced and the converter is started, an excessive power supply current may flow if the maximum voltage on the AC side of the converter is low. The conditions for reducing the maximum voltage on the AC side of the converter include (1) when the DC voltage at startup is small, and (2) when the voltage drop due to the dead time is set so that the power element is not short-circuited. In these cases. The AC side power supply of the converter is controlled by the current control Although it works to increase the voltage command, the AC voltage of the converter is considerably lower than the power supply voltage because the underlying DC voltage is small. Thus, the difference voltage between the power supply voltage and the converter AC side voltage is applied to the AC reactor having relatively small impedance, and an excessive current flows.

For example, in the case of receiving 200 V, the diode rectified voltage charges up to the peak of the power supply voltage, so that V dc = 283 V. In this DC voltage, when the amplitude ratio is 1 (the ratio of the peak value of the modulated wave to the peak value of the carrier wave is 1), the voltage on the AC side of the comparator is V dc Z 2-14 1.5 V. Note that the effective value of the line voltage is 3/2 times, that is, 173 V, so that a difference voltage of 27 V is applied to the AC reactor. As a result, an excessive power supply current flows. Also, if the voltage drop due to the dead time provided so that the power element is not short-circuited even if the amplitude ratio is increased to 1 or more, the AC side voltage of the converter becomes small, and excessive power supply current tends to flow. When the DC voltage increases, the converter AC side voltage increases and the difference voltage decreases, so that the excess current converges. For this reason, when the voltage drop due to the dead time is large, the effect of suppressing the excessive power supply current may not be sufficient simply by starting with a small power supply current amplitude command. Disclosure of the invention

The present invention has been made in consideration of the above-described problems in the conventional technology.

The converter control device according to the present invention generates a chopper drive signal for operating the converter in a cantilever manner and a PWM drive signal for operating the converter in PWM, and constructs a main circuit of the converter by using one of the drive signals. Output to the switching element. According to this control device, the chopper operation and the PWM operation can be appropriately switched and the converter can be operated while using the same converter main circuit. For this reason, when starting the converter, the present control device can output the Chituba drive signal to the switching element, and can output the PWM drive signal to the switching element after the DC output voltage is boosted. Therefore, when switching to PWM operation, the voltage across the AC reactor can be reduced, so that no excessive power supply current flows to the AC side.

Next, in the converter control method according to the present invention, when the converter is started, the converter is operated in a chopper, and after the DC output voltage is boosted, the converter is operated in PWM. According to this control method, similarly to the converter control device according to the present invention, when switching to the PWM operation, the voltage across the AC reactor can be reduced, so that an excessive power supply current does not flow to the AC side.

Further, the converter according to the present invention is operated by the control device or the control method as described above. Therefore, at the time of startup, there is no inconvenience that the switching element is destroyed or malfunctions due to an excessive power supply current. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a control block diagram showing one embodiment of the present invention.

FIG. 2 is a detailed block diagram of the PWM converter control means shown in FIG. Figure 3 shows an example of supplying a one-phase chopper gate voltage to the converter main circuit.

FIG. 4 is a diagram showing a method of creating the one-phase chopper signal shown in FIG.

FIG. 5 is an operation mode diagram of how the power supply current ir flows in FIG. FIG. 6 is a diagram showing how a main circuit current flows in each mode of FIG. FIG. 7 is a simulation diagram of the boosting operation at the time of the one-phase filter control in FIG.

FIG. 8 is a flowchart showing a control sequence in the embodiment of the present invention.

FIG. 9 is an operation waveform diagram of an operation mode and a DC voltage in the embodiment of the present invention. FIG. 10 is a flowchart showing a control sequence in another embodiment of the present invention.

FIG. 11 is an operation waveform diagram of an operation mode and a DC voltage in another embodiment of the present invention.

FIG. 12 is a diagram showing an example of supplying a three-phase Chiborg gate voltage to the converter main circuit.

FIG. 13 is a diagram showing a method of creating the three-phase chitsubasa signal shown in FIG. FIG. 14 is a simulation diagram of the boosting operation when the three-phase shared control shown in FIG. 12 is performed.

FIG. 15 is a configuration diagram of a single-phase PWM converter to which the present invention is applied. FIG. 16 is a configuration diagram of an active filter to which the present invention is applied. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, AC power is supplied from an AC power supply 1 to a converter 3 via an AC reactor 2, and this AC power is converted into DC power in the converter 3, and is supplied to a smoothing capacitor 4 and a load 5. Supplied. After the AC power supply 1 is turned on, the contactor 6 is in the open state, and the charging current flows to the smoothing capacitor via the inrush current suppression resistor 7. After this, the DC voltage V dc When charged to or near the diode rectified voltage, contactor 6 closes and shorts inrush current suppression resistor 7. That is, the rush current to the smoothing capacitor when charging up to the diode rectified voltage is suppressed by the contactor 6 and the rush current suppressing resistor 7. On the other hand, in the case of the control device, when the power supply 1 is turned on, the control circuit 8 including a microcomputer starts operating. Next, when the start command is turned on from the beginning, the switch 10 is switched to the chopper signal by the gate signal switching means 9. In addition, the converter 3 is operated by the chopper operation through the gate circuit 12 by the chopper operation gate signal generation means 11 to perform the boost operation. Thus, the chopper operation is performed from the beginning, but the contactor 6 is in the open state, and the charging current flows to the smoothing capacitor via the inrush current suppressing resistor 7. Thereafter, when the DC voltage Vdc is charged to or near the diode rectified voltage, the contactor 6 closes and short-circuits the inrush current suppressing resistor 7, and thereafter the voltage is increased only by the chopper control.

Next, the voltage across the smoothing capacitor is detected by the DC voltage detector 13 and this output is monitored.When the DC voltage reaches the DC voltage during the normal operation of the PWM converter, all the gate signals are cut off once. Switch switch 10 to PWM signal. This switches to the PWM converter operation control. The PWM converter operation control means 14 creates the power supply current amplitude command so that the actual DC voltage detection value matches the DC voltage command Vdc *. In addition, the voltage detector 15 that insulates and detects the AC voltage and the power phase detection means 16 detects the R-phase power voltage phase Θr and creates a current command with a power factor of 1 based on this. are doing. Further, a PWM signal is output so that the actual power supply current detected by the current detector 17 matches the current command.

The embodiment described above is an example in which the fever control is started immediately after the power is turned on. As described above, the same operation is performed even after the diode is rectified and the control is performed. First, when the power is turned on while all the gate signals of converter 3 are cut off, the insulated gate bipolar transistor (hereinafter referred to as IGBT) of converter 3 is turned off, so that a diode rectifier circuit is formed. It becomes a three-phase rectified voltage. In this case as well, after the AC power supply 1 is turned on, the smoothing capacitor is charged through the inrush current suppression resistor 7, and when the DC voltage V dc is charged to near the diode rectification voltage, the contactor 6 closes and the inrush current suppression resistor 7 is activated. Short circuit.

Next, when a start command is input, the gate signal switching means 9 switches the switch 10 to the chopper signal and operates the converter 3 as a chopper to increase the DC voltage. Next, when the voltage between both ends of the smoothing capacitor reaches the DC voltage at the time of the steady operation of the PWM comparator, the gate signal is temporarily cut off and switch 10 is switched to the PWM signal. This switches to PWM converter operation control.

Next, a detailed block diagram of the PWM converter operation control means 14 is shown in FIG. The amplitude command I * of the power supply current is output via the compensation means 18 for the DC voltage deviation (proportional + integral). The current command generating means 19 calculates the following equation and outputs three-phase instantaneous current commands i _u *, iv *, i _w *.

i u * = I * «sin0 r

i v * = I * .sin (Θ r-2 π / 3)

i w * = — (i u * + i v *)

Next, the current control means 20 outputs a voltage command Vc * of the three-phase converter so that the actual power supply current ir, is, it matches the current command, and outputs a PWM signal corresponding to the voltage command to the PWM command. Output by the signal generation means 21. Next, an embodiment and operation of the chimney driving gate signal generating means 11 which is a main part of the present invention will be described in detail.

FIG. 3 shows a detailed circuit configuration diagram of the converter 3. (i = U, V, W, j = N, P) are gate signals used to create a drive signal for controlling IGBT Ti on / off. In the U phase, the IGBTT _UP of the positive arm and the reflux diode D _UP are connected in parallel in opposite directions. Similarly, the negative arm has IGBTT _UN and reflux diode D _UN connected in parallel in opposite directions. The positive arm element and the negative arm element are connected in series. The same applies to the V and W phases. Therefore, given a gate voltage of Chiyotsuba only T _UN, driving all other IGBT is in a state of OFF.

Figure 4 shows the gate signal output method. In Fig. 4, a gate signal is output by comparing a triangular wave and a modulated wave. By setting the modulation wave level of the transistor T _UN to be larger than the lower limit of the triangular wave, the butterfly gate signal S _UN is created. Also, the gate signal of OFF is generated by setting the modulation wave level of the other transistors smaller than the lower limit of the triangular wave.

FIG. 5 shows the operation mode of the flow of the R-phase power supply current ir when the gate signal shown in FIG. 3 is given, and FIG. 6 shows the flow of the main circuit current in each mode. The operation mode changes according to the three phases of the power supply voltage. For example T _UN-on in mode 1, to flow from the power supply voltage V _R in the direction of the low supply voltage _{_{V s, V R _ Lu- T}} UN -D VN - L v - AC in the path of V _s _ V _R Riata torr Lu, current flows in the L _v, energy is stored. _{_{Lu- D UP - - C- D VN}} - Lv- V s - V routes the charging current to the smoothing capacitor C of the _R boosts flows to the next, V _R when off Chiyoppa. In addition, as shown in FIG. 5, the charging current flows from mode 1 to mode 4, and mode 5 and mode 6 do not flow. Next, Fig. 7 shows the simulation results of the boosting operation in the modes shown in Figs. In the section up to 40 ms when receiving three-phase 200 V, the DC voltage is approximately 280 V in the diode rectification mode. Thereafter, the chopper operation is started from 40 ms to increase the pressure. The simulation conditions are as follows: the Chitsubasa frequency is 1 kHz, the Chioppa on section is 100 με, and the off period is

9 0 0. The inductance of the AC reactor is 2 mH and the capacitance of the smoothing capacitor is 1800 μF, which is a value for several kW load. The power supply current ir flows in the mode shown in FIG. In addition, in Fig. 7, the DC voltage during PWM

When the voltage is raised to about (340 V), the control is switched to PWM converter control. In FIG. 7, a power supply current of about 17 A peak flows during one cycle at the time of the start of the control of the fever. In contrast, in the prior art

Since a power supply current of about 100 A flows, an excessive current can be sufficiently suppressed according to the present embodiment. As a result, in the case of a converter for several kW load,

50 A rated power elements can be used. Also, the power supply current can be suppressed by shortening the on-period of the chopper signal (reducing the conduction ratio) in one cycle section at the start of the chopper control.

Next, FIG. 8 shows a flowchart of the control sequence in this embodiment, and FIG. 9 shows the relationship between the operation waveform of the DC voltage and the operation mode. The chopper control is started when the AC power is turned on. Also, the DC voltage V dc rises to almost the diode rectified voltage via the inrush current suppressing resistor 7 and thereafter is boosted by the chopper control. Therefore, at the start of the control of the butterfly, the inrush current suppressing resistor 7 can prevent an excessive charging current from flowing. Next, the DC voltage is monitored, and when it exceeds 340 V, all the gate signals are turned off, and then the control is switched to PWM converter control. to this Therefore, the PWM converter control is continued at about V dc = 340 V—constant. If the power supply current flowing at the time of PWM operation switching is smaller than the rated current of the switching element of the converter main circuit, before the DC voltage is boosted up to 340 V, the operation switches from Chituba operation to PWM operation. It is good to switch, Next, FIG. 10 shows a flowchart of a control sequence in another starting method, and FIG. 11 shows the relationship between the operation waveform of the DC voltage and the operation mode. In this method, the AC power is turned on with all gate signals turned off, and the DC voltage is first increased to the diode rectified voltage via the inrush current suppression resistor 7. After that, when the start command is turned on, the chitsubasa operation starts and the pressure rises. Next, the DC voltage is monitored, and when the voltage exceeds 340 V, all gate signals are temporarily turned off, and thereafter, the control is switched to PWM converter control.

As in the case of FIGS. 8 and 9, the operation may be switched to the PWM operation before the DC voltage is boosted to 34V. In addition, the Chitsubasa operation may be started before the DC voltage becomes 280 V.

As described above, according to the embodiment of the present invention, after the DC voltage is boosted by the chopper control and then switched to the PWM control, the converter AC voltage at the start of the PWM converter operation is equivalent to the power supply voltage. Large output can be obtained. As a result, since excessive voltage is not applied to the AC reactor, switching to PWM control has the effect of enabling smooth start-up without excessive current flow. Further, in FIG. 3 has been Chiyotsuba controlled negative arm of T _UN as a method of boosting, the same effect even if the T _UP of positive arms off the T _UN of Faichi beam is Chiyoppa operation. In addition, in FIG. 3, the chopper operates only in one phase, but the same effect can be obtained by operating the chopper in two or three phases, and the self-extinguishing of one of the positive and negative arms is performed. The arc element is operated as a squirt, and the self-extinguishing element of the other arm is turned off to raise the temperature. Pressure. Fig. 12 shows the main circuit configuration when the three-phase chopper signals are given, and Fig. 13 shows how to create the gate signals. Negative arms of the T _UN, TVN, given gate voltage of Chiyotsuba to T _WN, Trang register positive arm operates at all the off state. The gate signal is output by setting the modulation wave levels of the transistors T _UN , T _VN , and T _WN to be greater than the lower limit of the triangular wave, and comparing the output with the triangular wave to output the gate signal. The gate signal is turned off by setting the modulation wave level of the positive transistor to be smaller than the lower limit of the triangular wave. Fig. 14 shows the simulation result when the gate signal is controlled by this gate signal. The major difference from the one-phase fever in Fig. 7 is that the fundamental wave of the power supply current becomes a sine wave at a power supply power factor of 1, which has the effect of boosting the voltage with less power supply harmonics and no DC component. is there. In the simulation, the chamber control was started from the DC voltage after the diode rectification.However, the chamber control may be performed when the AC power supply 1 is turned on.Basically, before starting the PWM converter control at the time of steady operation. After the DC voltage between the smoothing capacitors is increased by chopper control of the converter, it is switched to PWM converter control.

Next, the present invention has been described with reference to the three-phase PWM converter. However, the general single-phase PWM converter shown in FIG. 15 and the general active filter for compensating the load side harmonic current shown in FIG. The same effect can be obtained by applying it to a general method of starting a voltage-source converter.

According to the present invention, the switching operation is performed in the converter main circuit before switching to the PWM converter control, and after the DC voltage is increased, the switching to the PWM converter control is performed. As a result, even when the input voltage drop of the converter due to the dead time is large or the like, switching to PWM control is performed with the DC voltage being large, so that the converter AC side voltage equivalent to the power supply voltage can be output. Since the voltage between the current reactors can be reduced, there is an effect that switching to regular PWM control is performed without excessive power supply current flowing.

In addition, as a method of boosting the DC voltage by the chopper operation, one of the positive or negative arms of the converter main circuit is operated by the chopper operation to boost the voltage. There is also an effect that it can be done.

Claims

The scope of the claims

1. A control device for a converter having a parallel circuit in which a switching element and a diode are connected in anti-parallel, and turning on and off the switching element by a drive signal to convert AC power to DC power.

A converter driving signal for operating the converter in a chopper and a PWM driving signal for operating the converter in a PWM manner, and outputting one of the driving signals to the switching element. .

2. The converter control device according to claim 1, wherein at startup of the converter, a drive signal is output to the switching element, and after a DC output voltage is boosted, a PWM drive signal is output to the switching element. A control device for a converter.

3. The converter control device according to claim 1,

A gutter operation gate signal generating means for generating a chopper gate signal for outputting the chopper drive signal, and a PWM comparator for generating a PWM gate signal for outputting the PWM drive signal A control circuit comprising: switch operation control means; and switch means for selecting any of the chopper gate signal and the PWM gate signal.

A gate circuit that receives a gate signal selected by the switch means and outputs one of the chopper drive signal and the PWM drive signal;

A converter control device, comprising:

4. The converter control device according to claim 3, wherein the switch means selects the gate signal for the chopper when the converter is started, and selects the gate signal for the PWM after the DC output voltage is boosted. To do A converter control device characterized by the above-mentioned.

5. The converter control device according to claim 2, wherein, at the time of the startup, the DC output voltage is boosted by diode rectification after turning off the switching element by shutting off the drive signal, and boosting the switching element by diode rectification. A converter control device for outputting a chopper drive signal to said switching element.

6. The converter control device according to claim 2, wherein the starter drive signal is output to the switching element immediately after the AC power is turned on at the time of starting.

7. The converter control device according to claim 1, wherein the converter is a converter for converting three-phase AC power into DC power, and the chopper driving signal is output from one of three phases. A control device for a converter, wherein the output is provided to only one of the switching elements of the arm and the lower arm.

8. The converter control device according to claim 1, wherein the converter is a converter that converts three-phase AC power into DC power, and the chopper driving signal is a switching signal of one of an upper arm and a lower arm of a plurality of phases. A converter control device characterized by being output to a device.

9. A method of controlling a converter, which has a parallel circuit in which a switching element and a diode are connected in anti-parallel and converts ON / OFF of the switching element to convert AC power to DC power.

A method of controlling a converter, comprising: operating the converter at a start-up time when the converter is started; and performing a PWM operation after a DC output voltage is increased.

10. The method of controlling a converter according to claim 9, wherein at the time of starting, After the DC output voltage is boosted by diode rectification, a chitsubasa operation is performed.

11. The converter control method according to claim 9, wherein a chopper operation is performed immediately after the AC power is turned on at the time of starting.

12. The control method of a converter according to claim 9, wherein the converter is a converter for converting three-phase AC power into DC power, and the upper arm and the lower arm of any one of the three phases during the operation of the chitsubasa. A control method for a converter, characterized in that only one of the switching elements is turned on / off.

13. The method of controlling a converter according to claim 9, wherein the converter is a converter that converts three-phase AC power into DC power, and when the chopper is operated, any one of the upper arm and the lower arm of the multi-phase is switched. A method for controlling a computer, comprising: performing on / off control of an element.

14. A converter that has a parallel circuit in which a switching element and a diode are connected in anti-parallel, and that converts the AC power into DC power by controlling the switching element on / off by a drive signal.

A controller that generates a chopper drive signal for operating the converter in a cantilever manner and a PWM drive signal for operating the converter in a PWM manner and outputs one of the drive signals to the switching element. And a converter.

15. The converter according to claim 14, wherein the control device outputs a drive signal to the switching element when the converter is started, and outputs a PWM drive signal after the DC output voltage is increased. A converter for outputting to the switching element.